A white LED has been applied to a backlight of TV, illumination or the like. Heat generation from an LED package becomes non-negligible in connection with achieving significant power. In the case where epoxy resin is used for a seating material, avoidance of yellowing due to the heat generation becomes quite difficult, and therefore silicone resin has been used for a seating material of white LED in place of the epoxy resin. The silicone resin used for the LED is broadly classified into two kinds including phenyl silicone resin and methyl silicone resin.
The phenyl silicone resin that is generally used has a satisfactory value for a refractive index, and while the resin is superior to the epoxy resin in resistance to thermal yellowing, is not enough to address achieving significant power of LED. The methyl silicone resin has, while the resin is superb in resistance to thermal yellowing, a low refractive index, and therefore has a poor light-extraction efficiency of LED.
Therefore, an eager wish has been expressed for a sealing material that can address achieving significant power of white LED and has both a high refractive index and good heat-resistant transparency, and a thermosetting resin composition used therefor.
Patent literature No. 1 discloses a thermosetting resin composition using silsesquioxane having excellent heat resistance and transparency and having both heat-resistant transparency and a high refractive index. The thermosetting resin composition comprises a polymer of organopolysiloxane and imperfect condensation structure silsesquioxane as commonly referred to as a double decker. Double-decker silsesquioxane is ordinarily different from structure of polysilsesquioxane having random structure obtained from an alkoxysilane hydrolytic condensation reaction. The composition has controlled structure, and therefore has high heat resistance.
Meanwhile, with regard to a thermoset material due to a combination of silsesquioxane and organopolysiloxane, a ratio of double-decker silsesquioxane being a hard component to an organopolysiloxane being a soft component is changed in compounding the thermosetting resin, thereby theoretically allowing adjustment of hardness of a hardened material from a rubbery material to a lenticular material.
Moreover, heat resistance has been recently required for an LED package itself, and in place of ordinary nylon-based polyphthalamide resin that has been frequently used so far, polyamide resin (PA9T: heat-resistant grade of polyamide) or a liquid crystal polymer (LCP) having excellent heat resistance has been adopted as various kinds of package materials.
In general, as a technique for improving adhesion, a silane coupling agent, or a compound prepared by introducing an epoxy group or an alkoxysilyl group into tetracyclosiloxane is known, but an effect is small to heat-resistant resin such as PA9T or LCP as described above. Moreover, attention has been recently attracted to a compound having an isocyanurate skeleton as such a material allowing an improvement in adhesion with the heat-resistant resin.
Patent literature No. 2 discloses as an adhesive an organopolysiloxane composition in which isocyanurate having an epoxy group is of addition hardening type. Moreover, patent literature No. 3 discloses a composition in which an alkoxysilyl group is further introduced into an isocyanuric ring skeleton having an epoxy group.
Patent literature No. 4 discloses isocyanuric skeleton-containing polysiloxane prepared by allowing an addition reaction of diallyl monoglycidyl isocyanurateto to Si—H-containing polysiloxane. Moreover, patent literature No. 5 presents isocyanuric skeleton-containing polysiloxane prepared by allowing an addition reaction of monoallyl glycidyl isocyanurate to polysiloxane having an SiH group in a side chain.